On Sun, 10 Feb 2008 00:08:33 GMT, Owen Duffy wrote:

I have found two common expressions for the Zo of a two wire line in
space.

One expression is Zo=276log(D/d).

The second is Zo=120acosh(D/d).

Hi Owen,

I have the following expressions found in "Reference Data for Radio
Engineers," 22-22 Transmission Lines:

Zo = 120 acosh(D/d)
Zo ~ 276 log(2D/d)
Zo ~ 120 Ln(2D/d)

where the symbol ~ means "approximately equal to."

73's
Richard Clark, KB7QHC